Devices which include a liquid in which flakes resembling snow fall slowly through a liquid are, of course, old. In these devices, the snow has to be recirculated by shaking or overturning the device periodically; any figure shown in the scene is positioned within the liquid.
In my device, the snow is recirculated by a type of pump which is within the scene, but is substantially invisible. Thus, the unit does not have to be turned or shaken to keep it operating. In addition, any figure or object depicted in the scene is not subject to contact with the liquid. This is valuable because, for example, when a bottle is being displayed, its label does not get constantly soaked, resulting in eventual deterioration.